Medical device locking mechanisms and related methods and systems

ABSTRACT

Medical device locking mechanisms and related methods and systems. In some embodiments, the medical device may comprise an outer surface defining one or more fastener openings configured for receiving one or more fasteners. The one or more fasteners may comprise an upper surface configured to be engaged by a component of the locking system to prevent fastener backout. A plurality of petal structures may be configured to be selectively expanded or contracted to engage the head portion and retain the at least one fastener within the fastener opening to prevent the fastener from backing out of the fastener opening. A biasing member may selectively engage the plurality of petal structures to either expand or contract the plurality of petal structures to facilitate locking the fastener(s) in place within the device.

RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 11/875,072, filed on Oct. 19, 2007, and titled“CERVICAL PLATE LOCKING MECHANISM AND ASSOCIATED SURGICAL METHOD”, whichis a continuation-in-part of U.S. patent application Ser. No.11/804,545, filed on May 18, 2007, and titled “CERVICAL PLATE LOCKINGMECHANISM AND ASSOCIATED SURGICAL METHOD.” Both of the foregoingapplications are hereby incorporated by reference herein in theirentireties.

FIELD OF THE INVENTION

Some embodiments disclosed herein relate generally to locking and/oranti-backout mechanisms for various medical devices and/or implants, andrelated methods. For example, various features and/or components ofembodiments disclosed herein may be incorporated into and/or used inconjunction with various implants, including cervical plates,thoracolumbar fixation plates, anterior lumbar fixation plates,standalone interbody devices, bone fracture fixation plates, pediclescrew couplers, such as pedicle screw tulips, and the like.

Some embodiments may comprise one or more novel locking screws and anovel plate that works cooperatively therewith. The locking mechanism,the one or more novel locking screws, and/or a novel plate or other suchimplants may be used for the fixation/stabilization of the spine, suchas the cervical spine. Alternatively, some embodiments may be configuredfor the fixation/stabilization of the lumbar spine, the sacral spine,and/or the placement of bone grafts, biocompatible inserts, and thelike. Still other embodiments may be used for the fixation/stabilizationof other anatomical structures and/or non-anatomical structures.

BACKGROUND OF THE INVENTION

The vertebrae of the human spine are generally arranged in a column,with an intervertebral disc disposed between each. These intervertebraldiscs transmit forces and perform a “cushioning” function. As a resultof the stresses and strains continuously applied to the intervertebraldiscs, as well as disease, degeneration and/or deformity is relativelycommon. Typically, diseased, degenerated, and/or deformed intervertebraldiscs are treated by removal and the insertion of an implant, anatomical(i.e., a bone graft) or mechanical (i.e., a biocompatible insert), inthe associated intervertebral space. The adjacent vertebrae arepreferably immobilized using a plate, such as a cervical plate, duringbone graft or biocompatible insert placement and subsequently until theyfuse, for example.

Conventional cervical plates typically include a plurality of screwholes and one or more access holes, through which one or more bonegrafts or other biocompatible inserts are placed. These cervical platesmay span one or multiple levels, with a level defined by the presence ofan intervertebral space, and may be secured to the vertebrae of thespine using a plurality of bone screws. Absent some sort of lockingmechanism, these bone screws tend to reverse thread, or back out, overtime. This reverse threading or backing out is obviously problematic.Various locking mechanisms exist in the art for preventing reversethreading or backing out, and typically involve the use of polymericbushings, securing caps, securing cover plates, novel thread designs,and the like that prevent the bone screws from disengaging the vertebraeand/or cervical plate subsequent to installation. Many of these lockingmechanisms are ineffective, overly complicated, cumbersome to implement,and/or unnecessarily expensive. Thus, what is still needed in the art isa robust, simple, and inexpensive locking mechanism for cervical platesor other medical devices or implants incorporating screws or otherfasteners.

SUMMARY

In various exemplary embodiments, the present invention provides such arobust, simple, and inexpensive locking and/or anti-backout mechanismfor a screw and/or other fastener of a plate or other medical implant ordevice. Various embodiments may be elegant in design and effective inperformance. Some embodiments may utilize a plate with holes one or moreof which may comprise a locking lip structure and/or receiving well, andlocking screws that may incorporate a head portion having petalstructures that are outwardly biased prior to insertion via aninternally-disposed c-ring or another similar biasing member.Advantageously, in some embodiments, the lead-in torque of each of thelocking screws is less than the lead-out torque of each of the lockingscrews. Thus, reverse threading or backing out is prevented.

In a specific example of an embodiment of a fastener locking system fora medical device, such as, for example, a cervical plate, athoracolumbar fixation plate, an anterior lumbar fixation plate, anintervertebral device, a bone fracture fixation plate, or a pediclescrew coupler, the system may comprise an outer surface defining atleast one fastener opening in the outer surface configured for receivinga fastener. The at least one fastener opening may comprise a lipstructure positioned adjacent to the outer surface.

The system may further comprise at least one fastener, such as a lockingscrew, configured to be received in the at least one fastener opening.The at least one fastener may comprise a head portion comprising aplurality of petal structures configured to expand and contract toexpand and contract a size of the head portion.

The system may further comprise a biasing member, such as a c-ring,configured to be positioned within the plurality of petal structures toexpand a size of the head portion. The at least one fastener may beconfigured to contract to extend past the lip structure and then beexpanded by the biasing member within the head portion such that thepetal structures engage the lip structure to inhibit the at least onefastener from being removed from the at least one fastener opening.

In some embodiments, an upper portion of the lip structure may be angledinward towards a central axis of the at least one fastener opening suchthat the plurality of petal structures contracts as the head portion isinserted into the at least one fastener opening.

In another specific example of an embodiment of a fastener lockingsystem for a medical device, the system may comprise a medical devicecomprising an outer surface defining at least one fastener opening inthe outer surface configured for receiving a fastener. The at least onefastener opening may be defined at least in part by a plurality of petalstructures configured to expand and contract.

The system may comprise a biasing member configured to be positionedaround the plurality of petal structures to provide an inward bias tothe plurality of petal structures and contract a size of the at leastone fastener opening.

The system may further comprise at least one fastener configured to bereceived in the at least one fastener opening. The at least one fastenermay comprise a head portion configured to be retained in the at leastone fastener opening by the plurality of petal structures and thebiasing member.

In some embodiments, the head portion may comprise an upper surface, andthe plurality of petal structures may be configured to engage the uppersurface after the biasing member has been positioned around theplurality of petal structures with the at least one fastener in the atleast one fastener opening.

In some embodiments, the biasing member may be configured to bepositioned concentrically around the plurality of petal structures.

In still another specific example of a fastener locking system for amedical device, the system may comprise a medical device comprising anouter surface defining one or more fastener openings configured forreceiving a fastener. The system may comprise at least one fastenerconfigured to be received in the at least one fastener opening. The atleast one fastener may comprise a head portion comprising an uppersurface.

The system may further comprise a plurality of petal structuresconfigured to be selectively expanded or contracted to engage the headportion and retain the at least one fastener within the at least onefastener opening to inhibit the fastener from backing out of the atleast one fastener opening. A biasing member may be configured toselectively engage the plurality of petal structures to either expand orcontract the plurality of petal structures between an open configurationin which the at least one fastener is able to be removed from the atleast one fastener opening and a closed configuration in which the atleast one fastener is at least inhibited from being removed from the atleast one fastener opening. The plurality of petal structures may beconfigured to engage the upper surface of the at least one fastener inthe closed configuration.

In some embodiments, the plurality of petal structures may be part (insome embodiments an integral part) of the head portion. In some suchembodiments, the biasing member may be configured to be positionedwithin the plurality of petal structures to expand a size of the headportion.

In some embodiments, the plurality of petal structures may togetherdefine a central driver bore configured to be engaged by a keyed tool.In some such embodiments, the central driver bore may comprise apolygonal shape.

In some embodiments, at least a subset of the plurality of petalstructures may comprise an inner groove configured to receive thebiasing member therein. In some such embodiments, each of the pluralityof petal structures may comprise an inner groove configured to receivethe biasing member therein.

In some embodiments, the plurality of petal structures may at leastpartially define the at least one fastener opening, and the biasingmember may be configured to be positioned around the plurality of petalstructures to provide an inward bias to the plurality of petalstructures.

In some embodiments, the at least one fastener opening may comprise alip structure positioned adjacent to the outer surface. As mentionedelsewhere herein, in some such embodiments, the petal structures may beconfigured to retain the fastener within the fastener opening beneaththe lip structure such that the lip structure contacts an upper surfaceof a head portion of the fastener.

The features, structures, steps, or characteristics disclosed herein inconnection with one embodiment may be combined in any suitable manner inone or more alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are illustrated and described herein with referenceto the various drawings, in which like reference numbers are used todenote like system components and/or method steps, as appropriate, andin which:

FIG. 1 is an exploded perspective view of one exemplary embodiment ofthe cervical plate locking mechanism of the present invention (beinginstalled using a keyed screwdriver or the like), the cervical platelocking mechanism including both novel plate and novel locking screwdesigns;

FIG. 2 is an exploded perspective view of one exemplary embodiment ofthe novel locking screw design of FIG. 1, the locking screw including ahead portion that incorporates a plurality of petal structures that areoutwardly biased by an internally-disposed c-ring or the like;

FIG. 3 is a perspective view of the novel locking screw design of FIGS.1 and 2, the locking screw being in its “as inserted” state, with thec-ring being installed and the head portion being compressed;

FIG. 4 is a partial cross-sectional view of the cervical plate lockingmechanism of FIG. 1, the novel locking screw of FIGS. 1-3 in the processof being inserted into the novel plate of FIG. 1;

FIG. 5 is a partial cross-sectional view of the cervical plate lockingmechanism and locking screw of FIGS. 1-4 being fully inserted into thenovel plate of FIGS. 1 and 4;

FIG. 6 is a partial cross-sectional view of the cervical plate lockingmechanism and locking screw of FIGS. 1-5 after the locking screw hasbeen fully inserted into the locking plate and allowed to expandtherein;

FIG. 7 is a partial cross-sectional view of the cervical plate lockingmechanism of FIGS. 1, 4, and 5, the novel locking screws of FIGS. 1-5being inserted into the novel plate of FIGS. 1, 4, and 5 at variousexemplary angles;

FIG. 8 is a perspective view of another exemplary embodiment of thecervical plate locking mechanism of the present invention, the cervicalplate locking mechanism again including both novel locking plate andnovel screw (not illustrated) designs;

FIG. 9 is a partial perspective view of the cervical plate lockingmechanism of FIG. 7, the novel locking plate incorporating one or morescrew-receiving holes each including a plurality of petal structuresconfigured to engage and retain the novel screws (not illustrated);

FIG. 10 is an exploded perspective view of the cervical plate lockingmechanism of FIGS. 7 and 8, a novel screw being inserted into ascrew-receiving hole of the novel locking plate;

FIG. 11 is a perspective view of the cervical plate locking mechanism ofFIGS. 7-9, novel screws fully inserted into all of the screw-receivingholes of the novel locking plate;

FIG. 12 is a partial perspective view of the cervical plate lockingmechanism of FIGS. 7-10, novel screws fully inserted into all of thescrew-receiving holes of the novel locking plate; and

FIG. 13 is a partial cross-sectional view of the cervical plate lockingmechanism of FIGS. 7-11, a novel screws fully inserted into ascrew-receiving holes of the novel locking plate.

DETAILED DESCRIPTION OF THE INVENTION

As described above, in various exemplary embodiments, the presentinvention provides a robust, simple, and inexpensive locking and/oranti-backout mechanism. Some embodiments may be elegant in design andeffective in performance, and may utilize a plate with holes that eachincorporate a locking lip structure and/or receiving well. Associatedlocking screws may each incorporate a head portion having petalstructures that are outwardly biased prior to insertion via aninternally-disposed c-ring or the like. Advantageously, in someembodiments, the lead-in torque of each of the locking screws is lessthan the lead-out torque of each of the locking screws. Thus, reversethreading or backing out may be prevented.

FIG. 1 is an exploded perspective view of one exemplary embodiment of acervical plate locking mechanism 10 of the present invention (beinginstalled using a keyed tool, such as a keyed screwdriver 18 or thelike), the cervical plate locking mechanism 10 including both novelplate and novel locking screw designs, as are described in greaterdetail herein below. Specifically, the cervical plate locking mechanism10 comprises a plate 12 that is configured to be securely fixed toadjacent vertebrae of the cervical spine or the like via one or morelocking screws 14 and one or more c-rings 16. The keyed screwdriver 18may be used to drive the one or more locking screws 14 through the plate12 and into the adjacent vertebrae.

The plate 12 may comprise one or more screw-receiving holes 13 and,optionally, one or more access holes 15 for the placement of one or morebone grafts, biocompatible inserts, or the like. Preferably, the plate12 is manufactured from a biocompatible material and is sized such thatit achieves its intended purpose. Material, shape, and size selectionmay be selected according to the knowledge of those of ordinary skill inthe art. Each of the one or more locking screws 14 may comprise athreaded portion 17 and a head portion 19. The threaded portion 17 ofeach of the one or more locking screws 14 may be configured to passthrough the one or more screw-receiving holes 13 of the plate 12 andsecurely fix the plate 12 to the adjacent vertebrae. Thread selection iswell known to those of ordinary skill in the art.

The head portion 19 of each of the one or more locking screws 14 may beconfigured to securely engage each of the one or more locking screws 14with the plate 12. As described in greater detail herein below, the headportion 19 of each of the one or more locking screws 14 may be outwardlybiased by the c-ring 16, or by another similar biasing member or othermechanism or feature. Such mechanism or feature may be inserted and/orcompressed into the head portion 19 of a given locking screw 14. In someembodiments, the head portion 19 may expand automatically upon insertionof the c-ring 16.

The c-ring 16, or another comparable mechanism, and the head portion 19of the given locking screw 14 may be again compressed and subsequentlyallowed to expand as they are inserted into a given screw-receiving hole13 of the plate 12. More specifically, in some embodiments, the headportion 19 of a given locking screw 14 may be allowed to expand in thereceiving well of the given screw-receiving hole 13. This insertion maybe accomplished using, for example, a matching flat, triangle, square,star, hexagon, octagon, or other keyed screwdriver 18, as appropriate.Preferably, the shape of the outside of the head portion 19 of each ofthe locking screws 14 substantially corresponds to the shape of theinside of the associated receiving well, although this is not arequirement.

FIG. 2 is an exploded perspective view of one exemplary embodiment ofthe novel locking screw design of FIG. 1, the locking screw 14 includinga head portion 19 that incorporates a plurality of petal structures 20that are outwardly biased by the internally-disposed c-ring 16 or thelike. Locking screw 14 and/or its accompanying locking features may beincorporated into and/or used in conjunction with various implants, suchas cervical plates, thoracolumbar fixation plates, anterior lumbarfixation plates, standalone interbody devices, bone fracture fixationplates, pedicle screw couplers, such as pedicle screw tulips, and thelike.

As described above, c-ring 16, or other comparable mechanism, may beselectively inserted and/or compressed into the head portion 19 of agiven locking screw 14, and then allowed to expand. The c-ring 16, orother comparable mechanism, and the head portion 19 of the given lockingscrew 14 may then be compressed again and subsequently allowed to expandas they are inserted into a given screw-receiving hole 13 (FIG. 1) ofplate 12 (FIG. 1), or of another screw-receiving hole of another plateor other implant or medical device.

More specifically, the head portion 19 of the given locking screw 14 maybe allowed to expand in a receiving well of the given screw-receivinghole 13. This insertion may be accomplished using a matching flat,triangle, square, star, hexagon, octagon, or other keyed screwdriver 18(as shown in FIG. 1), as appropriate.

Preferably, the shape of the outside of the head portion 19 of each ofthe locking screws 14 at least substantially corresponds to the shape ofthe inside of the associated receiving well, although this is not arequirement. Accordingly, the head portion 19 of each of the lockingscrews 14 may comprise a plurality of concentrically-arranged petalstructures 20 that are disposed around a central driver bore 21, whichmay have a shape corresponding to that of the keyed screwdriver 18. Inone exemplary embodiment, the plurality of petal structures 20 may beformed by cutting concentrically-arranged slots into the head portion 19of the locking screw 14. Thus, the plurality of petal structures 20 may,in some embodiments and implementations, be integrally formed with thehead portion 19 of the locking screw 14. Alternatively, the plurality ofpetal structures 20 may be formed separately and then joined to the headportion 19 of the locking screw 14.

The material characteristics and/or configuration of the plurality ofpetal structures 20 may, in some embodiments, impart the plurality ofpetal structures 20 with an inherent outward bias, which bias in someembodiments may be independent of the c-ring 16 or other comparablemechanism, although this is not required.

In some embodiments, the plurality of petal structures 20 may define aninner groove 22 extending around an inner perimeter of head portion 19,such as around an exterior perimeter of central driver bore 21, as shownin FIG. 2. Inner groove 22 may be configured to receive and retain thec-ring 16 or other comparable mechanism within the head portion 19 ofthe locking screw 14. FIG. 2 illustrates the head portion 19 of thelocking screw 14 in an “unlocked” configuration, with the plurality ofpetal structures 20 being “open,” either due to the eventual insertionof the c-ring 16 or other comparable mechanism, or inherently. FIG. 3illustrates the head portion 19 of the locking screw 14 in a “locked”configuration, with the plurality of petal structures 20 being “closed,”either inherently or due to the eventual insertion of the head portion19 of the locking screw 14 into a receiving well. Thus, in someembodiments, the plurality of petal structures 20 may be configured tobe flexibly biased towards a locked/closed configuration such that thepetals 20 can be flexed open to an unlocked/open configuration toreceive c-ring 16 and then automatically revert to a locked/closedconfiguration with c-ring 16 therein. In some embodiments, the presenceof c-ring 16 within head portion 19 may partially flex petals 20 towardsan unlocked/open configuration (but not fully) so as to enlarge thediameter of head portion 19 and retain head portion 19 within a lockinghole of a device, such as cervical plate 12.

It can also be seen in FIGS. 2 and 3 that petal structures 20 eachpartially defines an upper surface of head portion 19 of locking screw14. In the depicted embodiment, this upper surface is flat. In thismanner, the upper surface of head portion 19 may be engaged with a lipstructure of a locking hole of a device, such as cervical plate 12, asdiscussed in greater detail below. FIGS. 2 and 3 further depict thatpetal structures 20 together define central driver bore 21 (as shown inFIG. 3) comprising a polygonal opening, and can be expanded by flexingpetal structures 20 (as shown in FIG. 2) such that petal structures 20no longer define the same bore opening. In this manner, a keyed tool,such as keyed screwdriver 18, may be used to expand central driver bore21 by inserting the keyed tool and rotating it. This may allow for thec-ring 16 to be inserted into inner groove 22. FIG. 3 also illustratesthat, in a closed configuration, petal structures 20 at leastsubstantially enclose c-ring 16 within head portion 19 to preventinadvertent removal of c-ring 16 after a locking screw 14 has been fullyengaged within a corresponding receiving hole 13.

FIG. 4 is a partial cross-sectional view of the cervical plate lockingmechanism 10 of FIG. 1, the novel locking screw 14 of FIGS. 1-3 in theprocess of being inserted into the novel plate 12 of FIG. 1. It shouldbe noted that the head portion 19 of the locking screw 14, andspecifically the lower, outer portion of each of the plurality of petalstructures 20, optionally incorporates a recessed or otherwise weakenedarea 24, or flexure, in order to facilitate the flexibility and/oroutward biasing of the plurality of petal structures 20 by the c-ring 16or other comparable mechanism, after it is inserted into the innergroove 22 that is manufactured into the middle, inner portion of each ofthe plurality of petal structures 20.

One or more of the one or more screw-receiving holes 13 of the plate 12or other such device may comprise an annular lip structure 26 throughwhich the head portions 19 of the locking screws 14 may be inserted(with a compression/expansion action). This annular lip structure 26 mayserve to retain the head portion 19 of the given locking screw 14 onceit is fully inserted and expanded, thereby preventing the reversethreading or backing out of the locking screw 14.

Optionally, the inner annular surface 28 of each of the screw-receivingholes 13 of the plate 12 may be curved in a generally concave manner, asshown in FIGS. 4-6, but shaped such that the lead-in torque of a givenlocking screw 14 is less than the lead-out torque or the locking screw14, i.e., the inner annular surface angles adjacent to the outer surface29 of the plate 12 (at the “top” and “bottom” of the lip structure 26)vary as experienced by an inserted locking screw 14 versus a removedlocking screw 14, with the “top” angle being greater (more vertical orsteep) and the “bottom” angle being smaller (more horizontal orshallow), for example.

As also shown in FIGS. 4-6, the portion of the lip structure 26immediately adjacent to the upper surface of petal structures 20 ispreferably angled slightly inward towards a center axis of centraldriver bore 21 to facilitate desirable feel and function of head portion19 of the locking screw 14 fitting into screw-receiving hole 13 andpreventing backout of locking screw 14 thereafter.

FIG. 5 is a partial cross-sectional view of the cervical plate lockingmechanism 10 of FIGS. 1 and 4, the novel locking screw 14 of FIGS. 1-4being fully inserted into the novel plate 12 of FIGS. 1 and 4. Again, itshould be noted that the head portion 19 of the locking screw 14, andspecifically the lower, outer portion of each of the plurality of petalstructures 20, optionally incorporates a recessed or otherwise weakenedarea 24, or flexure, in order to facilitate the flexibility and/oroutward biasing of the plurality of petal structures 20 by the c-ring 16or other comparable mechanism, after it is inserted into the innergroove 22 that is manufactured into the middle, inner portion of each ofthe plurality of petal structures 20. Each of the one or morescrew-receiving holes 13 of the plate 12 may comprise an annular lipstructure 26 through which the head portions 19 of the locking screws 14are inserted (with a compression-expansion action).

This annular lip structure 26 serves to retain the head portion 19 ofthe given locking screw 14 once it is fully inserted and expanded, asillustrated, thereby preventing the reverse threading or backing out ofthe locking screw 14. As described above, optionally, the inner annularsurface 28 of each of the screw-receiving holes 13 of the plate 12 iscurved in a generally concave manner, but shaped such that the lead-intorque of a given locking screw 14 is less than the lead-out torque orthe locking screw 14, i.e. the inner annular surface angles adjacent tothe outer surface 29 of the plate 12 (at the “top” and “bottom” of thelip structure 26) vary as experienced by an inserted locking screw 14versus a removed locking screw 14, with the “top” angle being greater(more vertical or steep) and the “bottom” angle being smaller (morehorizontal or shallow), for example.

FIG. 6 depicts head portion 19 of locking screw 14 after it has beenallowed to expand within receiving hole 13 by the expansion of c-ring16. As depicted in this figure, once this expansion takes place, anupper surface of head portion 19 of locking screw 14 contacts a lowersurface of lip structure 26 to retain locking screw 14 in place andprevent, or at least reduce the possibility of, backup.

Thus, some embodiments may be configured to have a first, fully openconfiguration in which the petal structures 20 are fully open to receivec-ring 16, a second, partially open configuration in which c-ring 16flexes petal structures 20 partially open, and a third, fully-closedconfiguration in which c-ring 16 is absent and petal structures 20 areable to fully compress together.

FIG. 7 is a partial cross-sectional view of the cervical plate lockingmechanism 10 of FIGS. 1, 4, 5, and 6 the novel locking screws 14 ofFIGS. 1-5 being inserted into the novel plate 12 of FIGS. 1, 4, 5, and 6at various exemplary angles relative to both the plate 12 and theunderlying vertebrae. In this embodiment, each of the receiving wellsmay be asymmetrical in shape such that the head portion 19 of each ofthe locking screws 14 snugly and securely engages the receiving well,although this is not necessarily illustrated. In other words, each ofthe receiving wells may be appropriately angled in the plate 12 in orderto receive each of the angled locking screws 14.

Referring to FIGS. 8-13, in another exemplary embodiment of a lockingmechanism 100 of the present invention, the locking mechanism 100 againcomprises both novel locking plate and novel screw designs, as aredescribed in greater detail herein below. Locking mechanism 100 alsocomprises a cervical plate locking mechanism although, as mentionedabove, this locking mechanism may be applied to a wide variety of otherdevices and implants, such as thoracolumbar fixation plates, anteriorlumbar fixation plates, standalone interbody devices, bone fracturefixation plates, pedicle screw couplers, such as pedicle screw tulips,and the like.

More specifically, the cervical plate locking mechanism 100 comprises alocking plate 102 that is configured to be securely fixed to adjacentvertebrae of the cervical spine or the like via one or more screws 104and one or more c-rings 106. The keyed screwdriver (not illustrated) isused to drive the one or more screws 104 through the locking plate 102and into the adjacent vertebrae. The locking plate 102 comprises one ormore screw-receiving holes 103 and, optionally, one or more access holes105 for the placement of one or more bone grafts, biocompatible inserts,or the like.

In some embodiments, the locking plate 102 may be manufactured from abiocompatible material and may be sized such that it achieves itsintended purpose. Material, shape, and size selection may be selected bythose of ordinary skill in the art. Each of the one or more screws 104may comprise a threaded portion 107 and a head portion 109. The threadedportion 107 of each of the one or more screws 104 may be configured topass through the one or more screw-receiving holes 103 of the lockingplate 102 and securely fix the locking plate 102 to the adjacentvertebrae. Thread selection may be as desired to those of ordinary skillin the art.

The head portion 109 of each of the one or more screws 104 is configuredto securely engage each of the one or more screws 104 with the lockingplate 102. As described in greater detail herein below, a plurality ofpetal structures 120 disposed about each of the screw-receiving holes103 may be inwardly biased by the c-ring 106. Petal structures 120 maybe incorporated into plate 102, or into another implant or devicecomprising screw-receiving holes. A c-ring 106, or another comparablemechanism may be expanded and subsequently allowed to contract aroundthe petal structures 120 as the head portion 109 of a screw 104 isdisposed in the receiving well of the given screw-receiving hole 103.This insertion may be accomplished using a matching flat, triangle,square, star, hexagon, octagon, or other keyed screwdriver, asappropriate. Preferably, the shape of the outside of the head portion109 of each of the screws 104 substantially corresponds to the shape ofthe inside of the associated receiving well, although this is not arequirement. Thus, in this exemplary embodiment, the plurality of petalstructures 120 and the c-ring 106 have been shifted from the one or morescrews 104 to the locking plate 102, accomplishing the same purposes.

It can be best seen in FIG. 13 that, once screw 104 is positioned in thereceiving well/hole 103 and c-ring 106 has been positioned about theplurality of petal structures 120, at least a portion of the lockingmechanism (namely, a portion of the petal structures 120) extends abovea top surface of screw 104 to secure screw 104 within hole 103 andprevent, or at least inhibit, backout of screw 104.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention, are contemplatedthereby, and are intended to be covered by the following claims.

1. A fastener locking system for a medical device, comprising: a medicaldevice comprising an outer surface, wherein the medical device definesat least one fastener opening in the outer surface configured forreceiving a fastener, and wherein the at least one fastener openingcomprises a lip structure positioned adjacent to the outer surface; atleast one fastener configured to be received in the at least onefastener opening, wherein the at least one fastener comprises a headportion comprising a plurality of petal structures configured to expandand contract to expand and contract a size of the head portion; and abiasing member configured to be positioned within the plurality of petalstructures to expand a size of the head portion, wherein the at leastone fastener is configured to contract to extend past the lip structureand then be expanded by the biasing member within the head portion suchthat the petal structures engage the lip structure to inhibit the atleast one fastener from being removed from the at least one fasteneropening.
 2. The fastener locking system of claim 1, wherein the medicaldevice comprises one of a cervical plate, a thoracolumbar fixationplate, an anterior lumbar fixation plate, an intervertebral device, abone fracture fixation plate, and a pedicle screw coupler.
 3. Thefastener locking system of claim 1, wherein the biasing member comprisesa c-ring.
 4. The fastener locking system of claim 1, wherein the atleast one fastener comprises at least one locking screw.
 5. The fastenerlocking system of claim 1, wherein the at least one fastener comprises athreaded portion.
 6. The fastener locking system of claim 5, wherein thethreaded portion is configured to engage with a bony structure of apatient.
 7. The fastener locking system of claim 1, wherein an upperportion of the lip structure is angled inward towards a central axis ofthe at least one fastener opening such that the plurality of petalstructures contracts as the head portion is inserted into the at leastone fastener opening.
 8. A fastener locking system for a medical device,comprising: a medical device comprising an outer surface, wherein themedical device defines at least one fastener opening in the outersurface configured for receiving a fastener, and wherein the at leastone fastener opening is defined at least in part by a plurality of petalstructures configured to expand and contract; a biasing memberconfigured to be positioned around the plurality of petal structures toprovide an inward bias to the plurality of petal structures and contracta size of the at least one fastener opening; at least one fastenerconfigured to be received in the at least one fastener opening, whereinthe at least one fastener comprises a head portion configured to beretained in the at least one fastener opening by the plurality of petalstructures and the biasing member.
 9. The fastener locking system ofclaim 8, wherein the biasing member comprises a c-ring.
 10. The fastenerlocking system of claim 8, wherein the head portion comprises an uppersurface, and wherein the plurality of petal structures is configured toengage the upper surface after the biasing member has been positionedaround the plurality of petal structures with the at least one fastenerin the at least one fastener opening.
 11. The fastener locking system ofclaim 8, wherein the biasing member is configured to be positionedconcentrically around the plurality of petal structures.
 12. A fastenerlocking system for a medical device, comprising: a medical devicecomprising an outer surface, wherein the device defines at least onefastener opening in the outer surface configured for receiving afastener; at least one fastener configured to be received in the atleast one fastener opening, wherein the at least one fastener comprisesa head portion comprising an upper surface; a plurality of petalstructures configured to be selectively expanded or contracted, whereinthe plurality of petal structures is configured to be either selectivelyexpanded or contracted to engage the head portion and retain the atleast one fastener within the at least one fastener opening to inhibitthe fastener from backing out of the at least one fastener opening; anda biasing member configured to selectively engage the plurality of petalstructures to either expand or contract the plurality of petalstructures between an open configuration in which the at least onefastener is able to be removed from the at least one fastener openingand a closed configuration in which the at least one fastener is atleast inhibited from being removed from the at least one fasteneropening, and wherein the plurality of petal structures are configured toengage the upper surface of the at least one fastener in the closedconfiguration.
 13. The fastener locking system of claim 12, wherein theplurality of petal structures are part of the head portion, and whereinthe biasing member is configured to be positioned within the pluralityof petal structures to expand a size of the head portion.
 14. Thefastener locking system of claim 13, wherein the plurality of petalstructures together define a central driver bore configured to beengaged by a keyed tool.
 15. The fastener locking system of claim 14,wherein the central driver bore comprises a polygonal shape.
 16. Thefastener locking system of claim 13, wherein at least a subset of theplurality of petal structures comprises an inner groove configured toreceive the biasing member therein.
 17. The fastener locking system ofclaim 14, wherein each of the plurality of petal structures comprises aninner groove configured to receive the biasing member therein.
 18. Thefastener locking system of claim 12, wherein the plurality of petalstructures at least partially define the at least one fastener opening,and wherein the biasing member is configured to be positioned around theplurality of petal structures to provide an inward bias to the pluralityof petal structures.
 19. The fastener locking system of claim 12,wherein the at least one fastener opening comprises a lip structurepositioned adjacent to the outer surface.
 20. The fastener lockingsystem of claim 12, wherein the biasing member comprises a c-ring.